Synergistic effects of antioxidant and silica on enhancing thermo-oxidative resistance of natural rubber: Insights from experiments and molecular simulations

In this work, the thermo-oxidative aging performance of antioxidant N-isopropyl-N'-phenyl-p-phenylenediamine (4010NA)/silica (SiO2)/natural rubber (NR) composite was evaluated by the variations of mechanical properties and chemical structure after aging at 100 degrees C. Compared with 4010NA/carbon black (CB)/NR composite, there existed significant synergistic effects between 4010NA and SiO2 on improving the thermo-oxidative stability of NR material. Then, by combining the results of experiments and molecular simulations, the synergistic stabilization mechanism in 4010NA/SiO2/NR composite could be attributed to the following comprehensive effects. Firstly, the incorporation of silica was capable of improving oxygen (O-2) barrier ability of NR and inhibiting the migration of 4010NA. Secondly, antioxidant 4010NA could be prior to terminate peroxy radicals, and its addition enabled 4010NA/SiO2/NR composite to be of an appropriately high cross-linking density due to a vulcanization accelerated effect. As a result, 4010NA/SiO2/NR composite exhibited more preeminent mechanical properties than 4010NA/NR and 4010NA/CB/NR composites during the thermo-oxidative aging process. This means that the combination of 4010NA and SiO2 can be exploited to prepare high performance NR composite with a facile operation. Furthermore, molecular simulation, as a theoretical method, may contribute to our understanding about structure-properties relationship for NR composite in depth. (C) 2019 The Authors. Published by Elsevier Ltd.